1. Field of the Invention
This invention relates to the production of materials can be used in the middle infrared (IR) range for laser technology and fiber optics.
2. Invention Disclosure Statement
The current state of the art in the production of materials with low absorbency in the IR range has focused on the process for making an improved end product rather than improving the infrared transmission of the starting material.
U.S. Pat. No. 5,186,870 describes a method for fabricating a fiber capable of transmitting IR light. This fiber is constructed of a silver halide compound that is extruded to form a single crystalline structure for a core and a polycrystalline structure for the cladding. This patent refers to the process of manufacturing the fiber. This patent does not reveal how to produce the actual silver halide composite so as to reduce the absorption of IR radiation.
U.S. Pat. No. 4,955,689 describes the actual fiber produced by the process in U.S. Pat. No. 5,186,870. The formulation used was a halide compound. This patent does not reveal how to produce the actual halide composite so as to reduce the absorption of IR radiation.
U.S. Pat. No. 5,575,960 describes a method of manufacturing an unclad fiber capable of transmitting IR. The process creates a fiber that is more durable and more evenly manufactured than conventional methods. This process does not reveal how to create a silver halide composite that is more transmitting and less absorbing of IR radiation than convention methods.
U.S. Pat. No. 5,575,959 describes a process for making an infrared window. This invention uses a zinc sulfide material with a gallium sulfide additive to produce a material that is highly transmitting to IR. This invention is limited to the making of IR windows using zinc sulfide. This patent also does not reveal how to improve the IR transmission of IR material.
U.S. Pat. No. 4,532,000 describes a method for making a crystal fiber through the melting of two polycrystalline fibers. This patent concentrates on the ability to make a fiber that is capable of IR transmission. This invention does not reveal how to make a fiber that has an improved IR transmission or how to improve the materials of the fibers.
U.S. Pat. No. 4,253,731 describes a method for making a silver chloride fiber with a silver bromide cladding capable of transmitting IR. This invention concentrates primarily on the fabrication of the fiber and not the fiber material. This invention does not reveal how to improve the transmittance of the fiber.
U.S. Pat. No. 4,678,274 describes an invention that improves the extrusion process for drawing fibers by integrating a rapid cooling mechanism. This cooling mechanism at the point of extrusion helps reduce the grain size of the fiber. A reduced grain size will reduce the scattering inside the fiber and therefore increase the transmission of the fiber. This invention, however, does not reveal how to increase the transmission of IR in the starting material prior to the drawing of the fiber.
U.S. Pat. No. 4,583,821 and U.S. Pat. No. 4,721,360 describe inventions that do improve the starting material used in IR transmission. The improvements, however, are only for the tensile and yield strength of the material not the transmission aspect of the material.
U.S. Pat No. 4,741,752 describes a process for treating a halide glass composition to improve infrared transmission at the wavelength of 2.7 microns by contacting a melt of the composition with dry oxygen without exposing the melt to ambient air. The improvement converts Fe (II) to Fe (III) and thereby reduces loss at the transmission wavelength attributable to Fe (II). The invention does not improve infrared transmission at 10.6 microns, which is the working wavelength of the CO2 laser.
It would be useful to have a process that can synthesize a material that allows greater transmission of IR in the 5 to 15 micron wavelength range than current processes allow.
It is an object of the present invention to describe a process for synthesizing single crystals of material that has a low absorbance in the 5 to 15 micron wavelength range.
It is another object of the present invention to provide single crystals of silver halides that have reduced absorbance in the 5 to 15 micron wavelength range.
It is a further object of the present invention to provide single crystals of silver halides that have improved transmittance at 10.6 microns, the working wavelength of the CO2 laser.
It is yet another object of the present invention to produce a fiber optic light guide for operation over medium IR wavelength range with low optic loss.
Briefly stated the present invention provides a method of synthesizing a material that has a low absorbance in the 5 to 15 micron wavelength range. The method is particularly useful for producing single crystals of silver halides for use in manufacturing fiber optic light guides with low optic loss in the medium IR range. This invention covers a totality of process steps and a sequential order in which they are carried out. The process of synthesizing this low IR absorbing material requires careful preparation of raw materials into suitable starting materials, followed by mixing specific ratios of the starting materials. A specific melting process then further purifies the mix. Once this initial purification process is completed, a specialized second purification process is performed on the material from the first process. This second purification process yields the proper material for crystallization via the Stockbarger-Bridgeman method. The final product becomes the starting material for an optical fiber or other optical component, like lenses or windows, with improved IR transmission.
The above and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings